<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
       .one{
           color: aqua;
           font-size: 32px;
       }
       .two{
           color: blue;
       }
         #a{
              color: red;
              font-size: 20px;
        #c{
                color: yellow;
            }
    </style>
</head>
<body>
    <!-- 命名不用数字 -->
    <p class="one" id="a">段落一</p>
    <p class="two" id="b">段落二</p>
    <p id="c">段落三</p>
    <div class="one">盒子一</div>
    <div class="two" >盒子二</div>
    <div >盒子三</div>
</body>
</html>